The Kneser graph \(KG_{p,k}\)  is the graph whose vertices correspond to the \(k\) -element subsets of a set of \(p\)  elements, where two vertices are joined if and only if the corresponding sets are disjoint. Properties of \(KG_{p,k}\)  include the following, with the eigenvalues due to Godsil and Royle [1]} and \(n^+\)  due to Godsil and Meagher (section 2.10 of [2]}).
\(\chi & = & p - 2k + 2, \mbox{ and hence } p \ge 2k, \mbox{ and } \omega = \left\lfloor \frac{p}{k} \right\rfloor ,\\n & = & {p \atopwithdelims ()k} \mbox{ and } n^+ = {p - 1 \atopwithdelims ()k} \mbox{ for even } k \mbox{ or } {p - 1 \atopwithdelims ()k - 1} \mbox{ for odd } k,\\2m & = & {p \atopwithdelims ()k}{p - k \atopwithdelims ()k}\) 
